This invention relates to control circuitry for an electronic musical instrument of a voltage-controlled type, that is, of a synthesizer type.
In a synthesizer type electronic musical instrument provided with means for generating control voltage waveforms and with voltage-controlled tone signal generating means including a voltage-controlled oscillator (hereinafter abbreviated as VCO), a voltage-controlled filter (hereinafter abbreviated as VCF) and a voltage-controlled amplifier (hereinafter abbreviated as VCA), for instance, a pitch determining voltage signal or first signal corresponding to the note of a key actuated on the keyboard and a trigger signal or second signal indicating the key actuation are coupled to the voltage-controlled tone signal generating means and the control voltage waveform generating means, respectively. Such an electronic musical instrument of a synthesizer type has a voltage divider network for producing the first signal which corresponds to the note of an actuated key and a storage capacitor for storing the first signal.
The conventional synthesizer type electronic musical instrument has a first group of key switches actuated by many keys on the keyboard in order to produce the first signal and a second group of key switches actuated also by many keys in order to produce the second signal. The provision of two key switch groups, however, apparently makes it difficult to enhance the reliability of the electronic musical instrument.
It is required of a synthesized type electronic musical instrument to produce musical sounds, even after the key-release, in accordance with control voltage waveforms. The storage capacitor should therefore retain the pitch determining signal for some time after the key-release.